Fibromatosis Colli of Infancy

Transverse ultrasound images of the right sternocleidomastoic (SCM) muscle and left (symptomatic side) shows diffuse enlargement of the left SCM with mixed echogenicity in a 2-month-old infant.

Facts: Fibromatosis Colli of Infancy

• Abnormal mass-like enlargement of sternocleidomastoic (SCM) muscle
• Born normal but develops SCM mass and/or torticollis within the first 4-8 weeks of life
• Associated with difficult delivery and intrauterine torticollis due to malposition
• Histology: collagen fibers and fibroblasts around atrophied muscle fibers
• Early diagnosis and treatment important because it can result in contracture
• Responds well to physiotherapy

Ultrasound Appearance

• US performed to exclude other diagnosis such as cervical lymphadenopathy, rhabdomyosarcoma, lymphoma, cystic hygroma or branchial cleft cyst
• Mass or fusiform enlargement of the SCM muscle
• Confined to muscle, no adjacent abnormalities of other soft tissues
• Variable echogenicity -- hyperechoic, hypoechoic, or mixed echogenicity

Reference:

Bedi DG, John SD, Swischuk LE. Fibromatosis colli of infancy: variability of sonographic appearance. J Clin Ultrasound 1998;26:345-348.